1. Field of the Invention
The present invention relates to a polishing agent which is especially used for chemically or mechanochemically polishing surfaces of hard but fragile materials such as GaAs (gallium-arsenite), GaP (galliumphosphorus) and InP (indium-phosphorus) compound semiconductor crystals of III-V into a strain-free and mirror-like surface with a high efficiency, and an apparatus for polishing using the polishing agent.
2. Description of the Related Art
For polishing a compound semiconductor crystal base such as GaAs and InP, a mixture solution of etching Br.sub.2 (bromine) and CH.sub.3 OH (methanol) has conventionally been used as a polishing agent, to obtain a high polishing efficiency and to secure complete crystallinity of the processed surface.
When said polishing agent is used, various advantages are obtained such that several to ten-and-several times as high an efficiency could be obtained as that obtained by a mechanical polishing such as so-called pitch polishing hitherto employed and that almost no deteriorated layer is detected on the processed portion.
However, Br.sub.2 (bromine) employed in the prior art polishing techniques, remarkably corrodes metals and produces unpleasant irritating smell. Therefore the polishing apparatus should be composed of limited kinds of materials and the poisonous nature of bromine requires special care and attention in handling. Thus, the polishing apparatus should be carefully equipped with devices for mixing liquids and treating waste liquids and exhaust gases.
Therefore, the polishing apparatus required various peripheral attachments and equipments and the high capital cost in the investment has been a fatal problem when a Br.sub.2 -CH.sub.3 OH solution is employed as polishing agent.
Further, the compound semiconductors are now considered to take the place of Si (silicon) wafers for making LSI (large scale semiconductor integrated circuitry apparatus) in the future and will be necessarily produced in a comparable or rather larger amount than that of Si wafers. In addition, since the mixed solution of Br.sub.2 and CH.sub.3 OH is apt to decompose within several ten minutes after mixing, it is troublesome to use the mixed solution. Even if full measures are taken for safety, hygiene and also for the complete setting of apparatus, the most careful and incessant attention is still necessary, and therefore the mixed solution is not suited to use for the mass production.